Additive manufacturing method for functionally graded material

ABSTRACT

A method for producing a functionally graded component layer-by-layer includes: depositing radiant-energy-curable resin on a build surface defined by a resin support, the resin containing filler including at least two groups of particles with different physical properties; allowing the filler to settle such that the groups of particles separate from each other, defining at least two regions within the resin; positioning a stage relative to the build surface so as to define a layer increment in the resin; selectively curing the resin using an radiant energy applied in a specific pattern so as to define the geometry of a cross-sectional layer of the component; moving the build surface and the stage relatively apart so as to separate the component from the build surface; repeating at least the steps of positioning and selectively curing for a plurality of layers, until the component is complete.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application of and claimspriority to and the benefit of U.S. Non-Provisional patent applicationSer. No. 16/231,539 filed on Dec. 23, 2018, the contents of which arehereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

This invention relates generally to additive manufacturing, and moreparticularly to methods for curable material handling in additivemanufacturing.

Additive manufacturing is a process in which material is built uplayer-by-layer to form a component. Stereolithography is a type ofadditive manufacturing process which employs a vat of liquidradiant-energy curable photopolymer “resin” and a curing energy sourcesuch as a laser. Similarly, DLP 3D printing employs a two-dimensionalimage projector to build components one layer at a time. For each layer,the projector flashes a radiation image of the cross-section of thecomponent on the surface of the liquid or through a transparent objectwhich defines a constrained surface of the resin. Exposure to theradiation cures and solidifies the pattern in the resin and joins it toa previously-cured layer. Other types of additive manufacturingprocesses utilize other types of radiant energy sources to solidifypatterns in resin.

Functionally graded materials vary in composition and structuregradually over volume, resulting in corresponding changes in theproperties of the material. The materials can be designed for specificfunction and applications. Various approaches based on the bulk(particulate processing), preform processing, layer processing and meltprocessing are traditionally used to fabricate the functionally gradedmaterials.

Functionally graded materials are useful in a variety of applicationswhere a single material is not suitable and where a discrete boundarybetween two different materials is not functional (for example, aceramic coating on top of a metal part; the coating tends to flake offdue to high mismatch in the coefficient of thermal expansion (CTE).

There is a need for a method of producing functionally graded materialsthrough additive manufacturing.

BRIEF DESCRIPTION OF THE INVENTION

At least one of these problems is addressed by an additive manufacturingmethod in which a resin has particles with different properties that areallowed to settle in different regions. The settled resin can be curedto create a functionally graded structure.

According to one aspect of the technology described herein, a method isprovided for producing a functionally graded component layer-by-layer,including the steps of: depositing resin on a build surface defined by aresin support, wherein the resin is radiant-energy-curable and containsfiller including at least two groups of particles with differentphysical properties; allowing the filler to settle such that the atleast two groups of particles separate from each other, so as to defineat least two regions within the resin; positioning a stage relative tothe build surface so as to define a layer increment in the resindeposited on the build surface; selectively curing the resin using anapplication of radiant energy in a specific pattern so as to define thegeometry of a cross-sectional layer of the component; moving the buildsurface and the stage relatively apart so as to separate the componentfrom the build surface; and repeating at least the steps of positioningand selectively curing for a plurality of layers, until the component iscomplete.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be best understood by reference to the followingdescription taken in conjunction with the accompanying drawing figuresin which:

FIG. 1 is a schematic side elevation view of an exemplary additivemanufacturing apparatus;

FIG. 2 is a schematic diagram of an exemplary scanned beam apparatus;

FIG. 3 is a cross-sectional view of a small portion of resin depositedin a vat, prior to a settling step;

FIG. 4 is a cross-sectional view of the resin shown in FIG. 3,subsequent to settling;

FIG. 5 is a cross-sectional view of a vat containing settled resin, witha stage positioned above the vat;

FIG. 6 is a cross-sectional view of the vat of FIG. 5 with a stagelowered into place for formation of a first layer;

FIG. 7 is a cross-sectional view of the vat of FIG. 5 with a stagelowered into place for formation of a second layer;

FIG. 8 is a cross-sectional view of the vat of FIG. 5 of the stagelowered into place for formation of a third layer; and

FIG. 9 is a cross-sectional view of the vat of FIG. 5 with the stageretracted, having three formed layers attached thereto.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the drawings wherein identical reference numerals denotethe same elements throughout the various views, FIG. 1 illustratesschematically an example of one type of suitable apparatus 10 forcarrying out an embodiment of an additive manufacturing method asdescribed herein. It will be understood that other configurations ofequipment may be used to carry out the method. Basic components of theexemplary apparatus 10 include one or more vats 11, a stage 14, aradiant energy apparatus 18, and (optionally) a vat transport mechanism20.

The vat 11 includes a floor 12 and a perimeter or walls 13 such that thevat is configured to receive a radiant-energy-curable resin R. In oneembodiment, the floor 12 is transparent or includes a portion orportions that are transparent. As used herein, the term “transparent”refers to a material which allows radiant energy of a selectedwavelength to pass through. For example, as described below, the radiantenergy used for curing could be ultraviolet light or laser light in thevisible spectrum. Non-limiting examples of transparent materials includepolymers, glass, and crystalline minerals such as sapphire or quartz.The floor 12 could be made up of two or more subcomponents, some ofwhich are transparent. The example shown here is a “bottom-upconfiguration”. In other embodiments (not shown), the vat 11 need not betransparent, as the radiant energy apparatus could be positioned acrossfrom the vat 11 (referred to as a “top-down” configuration).

The floor 12 of the vat 11 defines a build surface 22 which may beplanar. For purposes of convenient description, the build surface 22 maybe considered to be oriented parallel to an X-Y plane of the apparatus10, and a direction perpendicular to the X-Y plane is denoted as aZ-direction (X, Y, and Z being three mutually perpendicular directions).

While a vat 11 is used herein as an example to explain the principles ofthe invention, this is only one type of resin support that may be usedto define a build surface. For example, instead of a vat, a plate couldbe used, or a flexible foil, e.g. of the type used in conventional tapecasting.

The build surface 22 may be configured to be “non-stick”, that is,resistant to adhesion of cured resin. The non-stick properties may beembodied by a combination of variables such as the chemistry of thefloor 12, its surface finish, and/or applied coatings. In one example, apermanent or semi-permanent non-stick coating may be applied. Onenon-limiting example of a suitable coating is polytetrafluoroethylene(“PTFE”). In one example, all or a portion of the build surface 22 ofvat 11 may incorporate a controlled roughness or surface texture (e.g.protrusions, dimples, grooves, ridges, etc.) with nonstick properties.In one example, the floor 12 may be made in whole or in part from anoxygen-permeable material.

An area or volume immediately surrounding the location of the vat 11(when it is positioned for a curing step to take place) is defined as a“build zone”, denoted by a dashed-line box 23.

For purposes of simplified description, the exemplary vat 11 is shown asbeing statically positioned, with the entire build cycle describedherein occurring with the vat 11 in the build zone 23. Alternatively,the vat transport mechanism 20 may be provided for transporting vats 11into and out of the build zone 23 so that the vats 11 could be prepared(e.g. filled, emptied, and/or cleaned) at a location remote to the buildzone 23. In other words, the vats 11 could be handled as prefilled“cartridges”.

In the illustrated example, one possible vat transport mechanism 20 isshown in the form of a conveyor belt which extends laterally through thebuild zone 23. Other types of mechanisms suitable for this purposeinclude, for example, mechanical linkages, rotary tables, or roboteffector arms. It will be understood that the vats 11 may be moved intoor out of the build zone 23 from any desired direction.

Referring now to the components of apparatus 10, the stage 14 is astructure defining a planar surface 30 which is capable of beingoriented parallel to the build surface 22 when the vat 11 is positionedin the build zone 23. Some means are provided for moving the stage 14relative to the vat 11, and thus to the build surface 22, parallel tothe Z-direction. In FIG. 1, these means are depicted schematically as asimple actuator 32 connected between the stage 14 and a stationarysupport structure 34, with the understanding that devices such asballscrew electric actuators, linear electric actuators, delta drives,pneumatic cylinders, or hydraulic cylinders may be used for thispurpose. In addition to, or as an alternative to, making the stage 14movable, the floor 12 and/or the entire vat 11 could be movable parallelto the Z-direction.

New resin R and/or filler may be introduced into a vat 11 from a newmaterial reservoir 56 which may be movable into and out of the buildzone 23 by means of appropriate actuators. Means may be provided formixing the resin R to ensure the material is homogenous (including forexample, any or all of: new resin R, used resin R, new filler, usedfiller).

The radiant energy apparatus 18 may comprise any device or combinationof devices operable to generate and project radiant energy on the resinR in a suitable pattern and with a suitable energy level and otheroperating characteristics to cure the resin R during the build process,described in more detail below.

In one exemplary embodiment as shown in FIG. 1, the radiant energyapparatus 18 may comprise a “projector” 48, used herein generally torefer to any device operable to generate a radiant energy patternedimage of suitable energy level and other operating characteristics tocure the resin R. As used herein, the term “patterned image” refers to aprojection of radiant energy comprising an array of individual pixels.Non-limiting examples of patterned imaged devices include a DLPprojector or another digital micromirror device, a 2D array of LEDs, a2D array of lasers, or optically addressed light valves. In theillustrated example, the projector 48 comprises a radiant energy source50 such as a UV lamp, an image forming apparatus 52 operable to receivea source beam 54 from the radiant energy source 50 and generate apatterned image 57 to be projected onto the surface of the resin R, andoptionally focusing optics 58, such as one or more lenses.

The radiant energy source 50 may comprise any device operable togenerate a beam of suitable energy level and frequency characteristicsto cure the resin R. In the illustrated example, the radiant energysource 50 comprises a UV flash lamp.

The image forming apparatus 52 may include one or more mirrors, prisms,and/or lenses and is provided with suitable actuators, and arranged sothat the source beam 54 from the radiant energy source 50 can betransformed into a pixelated image in an X-Y plane coincident with thesurface of the resin R. In the illustrated example, the image formingapparatus 52 may be a digital micro-mirror device. For example, theprojector 48 may be a commercially-available Digital Light Processing(“DLP”) projector.

As an option, the projector 48 may incorporate additional means such asactuators, mirrors, etc. configured to selectively move the imageforming apparatus 52 or other part of the projector 48, with the effectof rastering or shifting the location of the patterned image 57 of thebuild surface 22. Stated another way, the patterned image may be movedaway from a nominal or starting location. This permits a single imageforming apparatus 52 to cover a larger build area, for example. Meansfor mastering or shifting the patterned image from the image formingapparatus 52 are commercially available. This type of image projectionmay be referred to herein as a “tiled image”.

In another exemplary embodiment as shown in FIG. 2, in addition to othertypes of radiant energy devices, the radiant energy apparatus 18 maycomprise a “scanned beam apparatus” 60 used herein to refer generally torefer to any device operable to generate a radiant energy beam ofsuitable energy level and other operating characteristics to cure theresin R and to scan the beam over the surface of the resin R in adesired pattern. In the illustrated example, the scanned beam apparatus60 comprises a radiant energy source 62 and a beam steering apparatus64.

The radiant energy source 62 may comprise any device operable togenerate a beam of suitable power and other operating characteristics tocure the resin R. Non-limiting examples of suitable radiant energysources include lasers or electron beam guns.

The beam steering apparatus 64 may include one or more mirrors, prisms,and/or lenses and may be provided with suitable actuators, and arrangedso that a beam 66 from the radiant energy source 62 can be focused to adesired spot size and steered to a desired position in plane coincidentwith the surface of the resin R. The beam 66 may be referred to hereinas a “build beam”. Other types of scanned beam apparatus may be used.For example, scanned beam sources using multiple build beams are known,as are scanned beam sources in which the radiant energy source itself ismovable by way of one or more actuators.

The apparatus 10 may include a controller 68. The controller 68 in FIG.1 is a generalized representation of the hardware and software requiredto control the operation of the apparatus 10, the stage 14, the radiantenergy apparatus 18, and the various actuators described above. Thecontroller 68 may be embodied, for example, by software running on oneor more processors embodied in one or more devices such as aprogrammable logic controller (“PLC”) or a microcomputer. Suchprocessors may be coupled to sensors and operating components, forexample, through wired or wireless connections. The same processor orprocessors may be used to retrieve and analyze sensor data, forstatistical analysis, and for feedback control.

Optionally, the components of the apparatus 10 may be surrounded by ahousing 70, which may be used to provide a shielding or inert gasatmosphere using gas ports 72. Optionally, pressure within the housing70 could be maintained at a desired level greater than or less thanatmospheric. Optionally, the housing 70 could be temperature and/orhumidity controlled. Optionally, ventilation of the housing 70 could becontrolled based on factors such as a time interval, temperature,humidity, and/or chemical species concentration.

The resin R comprises a material which is radiant-energy curable andwhich is capable of adhering or binding together the filler in the curedstate. As used herein, the term “radiant-energy curable” refers to anymaterial which solidifies in response to the application of radiantenergy of a particular frequency and energy level. For example, theresin R may comprise a known type of photopolymer resin containingphoto-initiator compounds functioning to trigger a polymerizationreaction, causing the resin to change from a liquid state to a solidstate. Alternatively, the resin R may comprise a material which containsa solvent that may be evaporated out by the application of radiantenergy. The uncured resin R may be provided in solid (e.g. granular) orliquid form including a paste or slurry.

Generally, the resin R should be flowable. According to the illustratedembodiment, the resin R is preferably a relatively low viscosity liquidthat is self-levelling. The resin R can be a liquid having a higherviscosity such that contact with the stage 14 is required to level theresin R. The composition of the resin R may be selected as desired tosuit a particular application. Mixtures of different compositions may beused.

The resin R may be selected to have the ability to out-gas or burn offduring further processing, such as the sintering process describedbelow.

The resin R incorporates a filler. The filler may be pre-mixed withresin R, then loaded into the new material reservoir 56. The fillercomprises particles, which are conventionally defined as “a very smallbit of matter”. The filler may comprise any material which is chemicallyand physically compatible with the selected resin R. The particles maybe regular or irregular in shape, may be uniform or non-uniform in size,and may have variable aspect ratios. For example, the particles may takethe form of powder, of small spheres, polyhedrons, or granules, or maybe shaped like small rods or fibers.

The composition of the filler, including its chemistry andmicrostructure, may be selected as desired to suit a particularapplication. For example, the filler may be metallic, ceramic,polymeric, and/or organic. Other examples of potential fillers includediamond, silicon, and graphite. Mixtures of different compositions maybe used.

The filler may include at least two groups of particles having differingphysical properties. For purposes of description, FIG. 3 shows anexample wherein a layer 80 of resin R includes two groups of particleslabeled “P1” and “P2”, respectively. The two groups of particles P1 andP2 vary in some property or combination of properties so as to give themdifferent “buoyancies” within the resin R. For example, this “buoyancy”will determine a particle's tendency to float to the top of the resinlayer, fall to the bottom of the resin layer, migrate to a specificstratum or vertical position, or maintain its position in a givenstratum or a specific vertical position. Examples of such propertiesaffecting buoyancy include: particle density, resin density, particlesize in any dimension, particle volume, particle shape, and/or thepresence of other particles and their various properties. For example,particles P1 and P2 could be spherical particles with identicaldiameters and thus identical volumes, but different densities. Asanother example, particles P1 and P2 could be spherical particles withidentical densities but different diameters and thus different volumes.The particles P1 and P2 need not have any specific buoyancy relative tothe resin R (e.g., positive, neutral, or negative). Rather, theirbuoyancies should be different from each other. The migration ofparticles within the resin will occur over time. The time constant (thetime required for a given particle to migration to a given position orstratum within the resin) will depend at least on the downward force ofgravity, the upward force of the resin displaced by the particle, andthe friction (including but not limited to adhesion, cohesion, stictionand drag force) between a given particle and any surrounding particlesand/or resin which will resist any motion in any direction.

FIG. 3 depicts the resin with particles P1 and P2 in a mixed condition.As will be described in more detail below, the differing forces actingon the particles P1 and P2 will cause them to seek different levels inthe resin R when given an opportunity to settle. For example, as shownin FIG. 4 the less buoyant particles P2 (shown as being physicallylarger for illustration purposes) will fall towards the bottom of a vat,while the more buoyant particles P1 will stay towards the top.

The filler may be “fusible”, meaning it is capable of consolidation intoa mass upon via application of sufficient energy. For example,fusibility is a characteristic of many available powders including butnot limited to: polymeric, ceramic, glass, and metallic.

The proportion of filler to resin R may be selected to suit a particularapplication. Generally, any amount of filler may be used so long as thecombined material is capable of flowing and being leveled, and there issufficient resin R to hold together the particles of the filler in thecured state.

Examples of the operation of the apparatus 10 will now be described indetail with reference to FIGS. 1, 3, and 4. It will be understood that,as a precursor to producing a component and using the apparatus 10, thecomponent 74 is software modeled as a stack of planar layers arrayedalong the Z-axis. Depending on the type of curing method used, eachlayer may be divided into a grid of pixels. The actual component 74 maybe modeled and/or manufactured as a stack of dozens or hundreds oflayers. Suitable software modeling processes are known in the art.

Initially, a vat 11 is prepared with resin R and positioned in the buildzone 23. If the vat 11 is a prefilled cartridge, then the steps of(optionally) applying a nonstick material to the build surface 22 andfilling the vat 11 with resin described below will have been completedoffline.

If the vat 11 is not provided as a prefilled cartridge, then the vat 11would need to be filled with resin. This filling step could be carriedout in the build zone 23, using the new material reservoir 56, or usinganother new material reservoir (not shown) in some other location. Asused herein, the term “filling” refers generally to the act ofdispensing, loading, or placing resin R into the vat 11 and does notnecessarily imply that the vat 11 be completely filled, or filled tomaximum capacity. Thus, the act of “filling” may be partial or complete.Optionally, as a preliminary step in the filling process, a nonstickmaterial may be applied to the build surface 22 prior to resinapplication. For example, a release agent such as polyvinyl alcohol(“PVA”) may be applied to the build surface 22 prior to each layer beingbuilt. In another example, a sacrificial layer having non-stickproperties may be applied. A nonstick film, e.g. a polymer sheet or filmcan be applied to the build surface 22. The film can be removed after alayer is cured.

When filling occurs within the build zone 23, the new material reservoir56 is used to apply resin R to the build surface 22. The quantity ofresin R applied may be sufficient for one layer 80 or for multiplelayers. As will be explained in more detail below, different methods maybe used to produce a functionally-graded component, depending on thefill level of the vat 11. It is noted that different vats 11 may befilled to different levels depending on the component geometry andchosen build style. Furthermore, the layer thickness does not have to beuniform from layer to layer. So even though the vat 11 is being filledfor just one layer at a time, if the layer thickness changes then sowould the vat fill level.

Optionally, different layers may comprise two or more different materialcombinations of resin R and/or filler. As used herein, the term“combination” refers to any difference in either of the constituents.So, for example, a particular resin composition mixed with either of twodifferent filler compositions would represent two different materialcombinations. For example, one layer may comprise a first combination ofresin R and filler, and a second layer may comprise a differentcombination of resin R and filler. Stated another way, any desired resinand any desired filler can be used for any given layer. The differentmaterials may be provided, for example, by providing multiple cartridgesor prefilled vats 11 filled with different materials, or by providingtwo or more new material reservoirs 56 of the type seen in FIG. 1.Different materials from different reservoirs may be mixed in aparticular vat 11, or they may be mixed at some other location beforesupplying them to a vat 11.

After the material is deposited, it is allowed to settle for apredetermined time interval. The differences in buoyancy and frictionbetween the different particles will cause less buoyant (e.g., denser orlarger or more uniform) particles to remain at and/or fall to thebottom, while more buoyant (e.g. less dense or smaller or moreirregular) particles to move to and/or remain at the top. For example,FIG. 4 shows an example where the groups of particles P1 and P2 shown inFIG. 3 have settled. The particles P1 and P2 are segregated from eachother, resulting in two distinct regions in the layer 80, e.g. a lowerregion 82 and an upper region 84. Where more than two different groupsof particles are used, they could form multiple stratified regions inthe layer 80. Optionally, settling may be encouraged by gently movingthe vat 11 (e.g., by low-displacement tilting or shaking).

After the material is deposited, the apparatus 10 is positioned todefine a selected layer increment. The layer increment is defined bysome combination of the depth within the vat 11 to which the resin isfilled and the operation of the stage 14. For example, the stage 14could be positioned such that the upper surface 30 is just touching theapplied resin R as shown in FIG. 4, or the stage 14 could be used tocompress and displace the resin R to positively define the layerincrement. The layer increment affects the speed of the additivemanufacturing process and the resolution of the component 74. The layerincrement can be variable, with a larger layer increment being used tospeed the process in portions of a component 74 not requiring highaccuracy, and a smaller layer increment being used where higher accuracyis required, at the expense of process speed.

In general, where a vat 11 is to be used to produce a singlefunctionally-graded layer at a time, the layer 80 of loaded resin in thevat 11 after coating should be approximately equal to the desired buildlayer (e.g. slice thickness) of the component 74 to ensure both materialregions 82, 84 are cured during exposure.

Once the resin R has been applied and the layer increment defined, theradiant energy apparatus 18 is used to cure a two-dimensionalcross-section or layer of the component 74 being built.

Where a projector 48 is used, the projector 48 projects a patternedimage 57 representative of the cross-section of the component 74 throughthe floor 12 to the resin R. This process is referred to herein as“selective” curing. It will be understood that photopolymers undergodegrees of curing. In many cases, the radiant energy apparatus 18 wouldnot fully cure the resin R. Rather, it would partially cure the resin Renough to “gel” and then a post-cure process (described below) wouldcure the resin R to whatever completeness it can reach. It will also beunderstood that, when a multi-layer component is made using this type ofresin R, the energy output of the radiant energy apparatus 18 may becarefully selected to partially cure or “under-cure” a previous layer,with the expectation that when the subsequent layer is applied, theenergy from that next layer will further the curing of the previouslayer. In the process described herein, the term “curing” or “cured” maybe used to refer to partially-cured or completely-cured resin R. Duringthe curing process, radiant energy may be supplied to a given layer inmultiple steps (e.g. multiple flashes) and also may be supplied inmultiple different patterns for a given layer. This allows differentamounts of energy to be applied to different parts of a layer.

The exposure to the radiant energy will cure both regions 82, 84 of thelayer 80 at the same time, so long as the total thickness of the layer80 is equal or less than the penetration depth of the radiant energy.This will result in the creation of a multi-material layer which isfunctionally graded.

Once curing of the first layer is complete, the stage 14 is separatedfrom the floor 12, for example by raising the stage 14 using theactuator 32.

Optionally, the component 74 and/or the stage 14 may be cleaned toremove uncured resin R, debris, or contaminants between curing cycles.The cleaning process may be used for the purpose of removing resin Rthat did not cure or resin R that did not cure enough to gel during theselective curing step described above. For example, it might be desiredto clean the component 74 and/or the stage 14 to ensure that noadditional material or material contamination is present in the finalcomponent 74. For example, cleaning could be done by contacting thecomponent 74 and/or the stage 14 with a cleaning fluid such as a liquiddetergent or solvent.

Subsequent to separation, the used vat 11 may be cleaned or otherwiserejuvenated and prepared for re-use by removing uncured resin R andother debris from the build surface 22. Non-limiting examples ofsuitable cleaning processes include brushing, abrading, scraping,vacuuming or blowing, absorbing, wiping, solvent rinsing, orcombinations thereof. The particular process or mechanism used to cleanor otherwise rejuvenate the vat 11 is not specifically relevant to thepresent invention. It will be understood that the process of cleaning orotherwise rejuvenating could be carried out in a remote location awayfrom the apparatus 10. The new material reservoir 56 would be used toapply resin R to the build surface 22 to ready it for curing again.

This cycle of preparing a vat 11, filling the vat 11 with resin R asneeded, allowing the particles to settle, incrementing a layer, andselectively curing is repeated until the entire component 74 iscomplete.

Where a scanned beam apparatus is used instead of a projector, theradiant energy source 62 emits a beam 66 and the beam steering apparatus64 is used to cure the resin R by steering a focal spot of the buildbeam 66 over the exposed resin R in an appropriate pattern. The cycle ofcycle of loading a vat 11, filling the vat 11 with resin R, andincrementing a layer is repeated. The radiant energy source 62 againemits a build beam 66 and the beam steering apparatus 64 is used tosteer the focal spot of the build beam 66 over the exposed resin R in anappropriate pattern. The exposed layer of the resin R is exposed to theradiant energy which selectively cures resin R as described above, andjoins it to the previously-cured layer above.

Optionally, a scanned beam apparatus may be used in combination with aprojector. For example, a scanned beam apparatus may be used to applyradiant energy (in addition to that applied by the projector) byscanning one or multiple beams over the surface of the uncured resin R.This may be concurrent or sequential with the use of the projector.

Either curing method (projector or scanned) and either build methodresults in a component 74 in which the filler (if used) is held in asolid shape by the cured resin R. In this component, no furthermigration of the filler particles is expected or desired, and thegradation created during the curing process is fixed. This component maybe usable as an end product for some conditions. Subsequent to thecuring step, the component 74 may be removed from the stage 14.

If the end product is intended to be composed of the filler (e.g. purelyceramic, glass, metallic, diamond, silicon, graphite, etc.), thecomponent 74 may be treated to a conventional sintering process to burnout the resin R and to consolidate the ceramic or metallic particles.Optionally, a known infiltration process may be carried out during orafter the sintering process, in order to fill voids in the componentwith a material having a lower melting temperature than the filler. Theinfiltration process improves component physical properties.

The method described above results in a component 74 comprising aplurality of layers, wherein each layer is functionally graded, orstated another way, a compositional gradient extends across each layer.As an alternative, multiple layers could be produced from a single fillof settled resin R in a vat 11. In this process, the less-buoyantparticles would be consumed during earlier cycles, thus resulting in afunctionally-graded structure in the completed component.

This process is illustrated with reference to FIGS. 5-9. FIG. 5illustrates a vat 11 having a build surface 22, containing resin R withtwo groups of particles P1 and P2 . Consistent with the descriptionabove, particles P2 are less buoyant and thus maintain a position closerto the build surface 22. A stage 14 is shown positioned above the vat11.

FIG. 6 shows the stage 14 positioned within the resin R at a selectedlayer increment above the build surface 22. The layer increment in theresin composition is such that this first layer 86 when cured, willinclude (exclusively or mostly) particles P2, as seen in FIG. 7.

FIG. 7 shows the stage 14 with the first layer 86 attached thereto andpositioned within the resin at a selected layer increment above thebuild surface 22. As some of the particles P2 have been consumed inproducing the first layer 86, a second layer 88, when cured, willinclude mostly particles P2, with some particles P1 included, as seen inFIG. 8. It should be noted that some mixing of the layers may occur whenthe stage is moved. If a mixed layer is desirable, it can be curedimmediately, as shown in FIG. 7. Otherwise, it may be necessary for sometime to pass to allow the layers to re-settle into their desired strata.

FIG. 8 shows the stage 14 with the first and second layers 86, 88attached thereto and positioned within the resin R at a selected layerincrement above the build surface 22. As essentially all of theparticles P2 have been consumed in producing the first layer 86 and thesecond layer 88, a third layer 90, when cured, will include solelyparticles P1, as seen in FIG. 9. The completed component 174 is thusfunctionally graded, with each layer including a different distributionof particles P1 and P2. As compared to the component 74 described above,the component 174 is a gradient extending over the entirety of thecomponent rather than over the layer increment.

Optionally, either of the methods of making a functionally gradedcomponent described above could be combined with conventional additivemanufacturing methods to produce a component having one or morefunctionally graded portions, regions, or sections, and one or morenon-graded portions, regions, or sections. For example, one or morelayers of the component 74 or 174 could be made using a build cycle inwhich the resin R is deposited with either no filler or with fillerincluding particles of substantially uniform physical properties, and/orwith the settling step omitted, such that settling and gradation doesnot occur.

The method described herein has several advantages over the prior art.In particular, it allows functionally graded materials to be producedthrough additive manufacturing.

The foregoing has described a method and apparatus for additivemanufacturing. All of the features disclosed in this specification(including any accompanying claims, abstract and drawings), and/or allof the steps of any method or process so disclosed, may be combined inany combination, except combinations where at least some of suchfeatures and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanyingclaims, abstract and drawings) may be replaced by alternative featuresserving the same, equivalent or similar purpose, unless expressly statedotherwise. Thus, unless expressly stated otherwise, each featuredisclosed is one example only of a generic series of equivalent orsimilar features.

The invention is not restricted to the details of the foregoingembodiment(s). The invention extends to any novel one, or any novelcombination, of the features disclosed in this specification (includingany accompanying claims, abstract and drawings), or to any novel one, orany novel combination, of the steps of any method or process sodisclosed.

What is claimed is:
 1. A method for producing a functionally gradedcomponent layer-by-layer, comprising the steps of: depositing resin on abuild surface defined by a resin support, wherein the resin isradiant-energy-curable and contains filler including at least two groupsof particles with different physical properties, wherein the resinsupport is a flexible foil defining the build surface; allowing thefiller to settle such that the at least two groups of particles separatefrom each other, so as to define at least two regions within the resin;positioning a stage relative to the build surface so as to define alayer increment in the resin deposited on the build surface; selectivelycuring the resin using an application of radiant energy in a specificpattern so as to define the geometry of a cross-sectional layer of thecomponent; moving the build surface and the stage relatively apart so asto separate the component from the build surface; and repeating at leastthe steps of positioning and selectively curing for a plurality oflayers, until the component is complete.
 2. The method of claim 1,further comprising, for each layer, repeating the step of depositing theresin and allowing the filler to settle, such that each layer isfunctionally graded.
 3. The method of claim 2, wherein each layerincludes a first, upper region containing particles of a first one ofthe groups and a second, lower region containing particles of a secondone of the groups.
 4. The method of claim 1, wherein the steps ofpositioning and selectively curing are repeated for a plurality oflayers without adding additional resin to the build surface, such thatthe component as a whole is functionally graded.
 5. The method of claim1, wherein the particles of the at least two groups have differentbuoyancies.
 6. The method of claim 1, wherein the particles of the atleast two groups have different frictional properties.
 7. The method ofclaim 1, wherein least a portion of the resin support is transparent andthe radiant energy is applied through the resin support.
 8. The methodof claim 1, wherein the particles of the at least two groups havediffering densities.
 9. The method of claim 1, wherein the particles ofthe at least two groups have differing volumes.
 10. The method of claim1, wherein the particles of the at least two groups have differingshapes.
 11. The method of claim 1, further comprising sintering thecomponent to burn out the cured resin and consolidate the filler. 12.The method of claim 11, further comprising infiltrating alower-melting-temperature material into the component during or aftersintering.
 13. The method of claim 1, wherein the application of radiantenergy is applied by projecting a patterned image comprising a pluralityof pixels.
 14. The method of claim 13, wherein the patterned image isshifted during the application of radiant energy.
 15. The method ofclaim 13, wherein additional radiant energy is applied by scanning atleast one build beam over the surface of the resin.
 16. The method ofclaim 1, wherein the radiant energy is applied by scanning a build beamover the surface of the resin.
 17. The method of claim 1, furthercomprising cleaning at least one of the component and the stage, whereinthe cleaning is carried out after the step of moving the build surfaceand the stage relatively apart.
 18. The method of claim 17, wherein thestep of cleaning includes contacting at least one of the component andthe stage with a cleaning fluid.
 19. The method of claim 1, furthercomprising executing a build cycle for at least one selected portion ofthe component, the build cycle including: depositing resin on the buildsurface, wherein the deposited resin is radiant-energy-curable andoptionally contains filler including particles with substantiallyuniform physical properties; positioning the stage relative to the buildsurface so as to define a layer increment in the deposited resin;selectively curing the deposited resin using an application of radiantenergy in a specific pattern so as to define the geometry of across-sectional layer of the component; moving the build surface and thestage relatively apart so as to separate the component from the buildsurface; and repeating at least the steps of positioning and selectivelycuring for a plurality of layers, such that selected portion of thecomponent is not functionally graded.